1. Field of the Invention
The present invention relates to a process and related plant for manufacturing the so-called “long” steel products (such as bars, wire, angle irons, beams and rails) without interruption from the continuous casting to the last rolling stand.
2. Description of Related Art
It is known to adopt for this type of production a continuous casting system with one or more lines for manufacturing blooms or billets which, possibly when still hot, feed a rolling mill with a number of stands adequate to the cross-section size of the final product. The finishing rolling can be obtained either by rolling a single billet at a time, or providing a continuous or endless line upon welding together the billet in head-tail succession upstream of the rolling mill. Also other methods are known to obtain an endless production, such as those disclosed in the patent EP 0761327 and in the international publication WO 00/71272, wherein the product from continuous casting is subjected to a temperature homogenization or equalization step throughout its cross-section, than heated and finally rolled in line.
A common feature to all the plants of this type according to the prior art is that the product from the continuous casting (bloom, billet, round bar etc.) undergoes a process of complete homogenization of temperature, in particular throughout the cross-section from the outer surface to the core before being rolled. A complete homogeneity/equalization of temperature between surface and core of the product has been deemed in the past to bring the advantage of a homogeneous elongation of the fibers which, having substantially all the same temperature, would show the same resistance to deformation.
On the contrary a constant technical prejudice has always been that a temperature difference between surface and core of the product would involve a non-homogeneous elongation, such as to affect the quality of the final product.
Still according to the prior art, at least two distinct rolling steps have been deemed to be necessary to obtain the final product, i.e. a first roughing step and a second finishing step, distinct from each other so that the bar to be processed is free from pinching along the whole pass between the two rolling steps.